Yui, who remarried and became a stepmother, lives daily with her husband and his son, who isn't much younger than she is. One day, she accidentally discovers the son masturbating and, filled with shock and confusion, scolds him. However, the boy insists, "My real mother gently touched my penis." His words leave Yui increasingly conflicted, and eventually, she allows him to hold her penis and grope her large breasts. His hot body instinctively devours her, making her juices flow uncontrollably, regardless of her intentions. Yielding to his clingy, affection-seeking behavior, Yui gradually forgets she's his stepmother and becomes addicted to the pleasure. Soon, a new desire begins to stir within her.